1. Field of the Invention
The present invention relates to a head-up display for a two-wheeled motorcycle.
2. Description of the Background Art
Various methods of allowing a running vehicle to detect the presence of another movable body such as a vehicle approaching thereto have been proposed. For example, Japanese Patent Laid-open No. Hei 2-216600 entitled xe2x80x9cTraffic Accident Prevention Methodxe2x80x9d describes a method of preventing a traffic accident of a relatively large vehicle having three or more wheels. According to this method, a receiver is mounted on the relatively large vehicle, wherein the receiver receives warning radio waves transmitted from a transmitter of another movable body, detects the presence of the movable body, and informs a driver of the detected result. This document does not describe a specific means of informing a driver of a warning state. Such a means is generally realized by an acoustic transmission method or an optical transmission method. One example using a head-up display, which is based on the optical transmission method, will be described below.
FIG. 8 is a view illustrating a four-wheeled vehicle provided with a prior art head-up display. A head-up display 100 includes a projector 102 built in an instrument panel 101. The projector 102 projects an image 104 on a plane, on the inner side of the vehicle, of a front window glass 103. The image 104 allows a driver to look therethrough, because the image 104 does not obstruct the visibility to the front side of the driver.
The techniques disclosed in the above-described document and shown in FIG. 8 are those applied to three-wheeled or four-wheeled vehicles. However, problems occur if the above-described head-up display is provided on a two-wheeled motorcycle different from a three-wheeled vehicle or four-wheeled vehicle.
Since a three-wheeled vehicle or four-wheeled vehicle is kept in a stable posture during running, it puts less burden on a driver, since the driver does not have to direct attention to preventing the three-wheeled vehicle or four-wheeled vehicle from turning over. However, since a motorcycle must be driven with its balance maintained during running, it puts a relatively large burden on a driver in order not to be turned over. From this viewpoint, it is difficult to mount a head-up display, which is designed for a three or four-wheeled vehicle, on a motorcycle.
It is therefore an object of the present invention to provide a head-up display suitable for a motorcycle. To achieve the above object, a head-up display for a motorcycle is provided which is adapted to inform a driver of traffic information by means of an image projected on a screen provided in front of a riding position of a driver. A visual field for a driver on the motorcycle and looking forwardly is divided into a central field and a peripheral field surrounding the central field. The image is located in the peripheral field on the screen.
The central field is defined such that an object in this field is clearly visible, and the peripheral field is defined such that an object in this field is dimly visible. Since the image is located in the peripheral field, the presence of the image can be recognized by a driver while not obstructing a desirable visibility to the front side of the driver. The driver can recognize, on the basis of the presence or absence of the image, whether or not attention should be directed to drive the vehicle.
The image may located at a central position of the peripheral field or a position offset to the central field from the central position of the peripheral field. With this configuration, the presence of the image located at a central position of the peripheral field or a position offset to the central field from the central position can be more easily recognized by a driver as compared with an image located at a position other than that described above.
The image may have a stripe or linear pattern. With this configuration, the presence of the image having a stripe or linear pattern can be more easily recognized by a driver as compared with an image having a dot pattern. The image having a stripe or linear pattern can be easily formed by a collection of dots. Accordingly, this configuration is advantageous in terms of production cost.
The image may have a stripe or linear pattern extending in the horizontal direction, and a length of the image is determined so that an angle formed between two lines extending from a point in the central field to both ends of the image becomes at least 20xc2x0.
An image having a pattern extending longer in the vertical direction tends to easily enter the eyes of a driver and thereby interfere with the driver""s view when the driver""s eyes move right and left. Since the image has a pattern extending longer in the horizontal direction, it does not interfere with the driver""s view when the driver""s eyes move right and left, and further, since an angle formed between two lines extending from a point in the central field to both ends of the image is set to at least 20xc2x0, the visibility can be enhanced.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.